Automatically Adding A Slate To 800 videos?

I soon will have hundreds, possibly thousands, of video clips (entries to a contest) that will need a beginning and end slate added to them.

How can I avoid manually doing this simple task? I'm playing around in Automator / QuickTime Pro for the first time right now. Any ideas or guidance is much appreciated! Thank you.

EDIT: I should also mention that the file formats will range from .mov, .wmv, .avi, .mpg. Pretty much anything is acceptable. So I realize I may need two steps if using QuickTime Pro. The first to convert to .mov and the second to perform the edit. If there's a way to keep it to one step that would be ideal.